I have been struggling with weight loss for 2-3 years now. I have been at about 128 lbs (5'3'' is height)

I go to gym 5 days a week. I do elliptical for 30 mins, then either legs or arms and abs workout, then another 10 min of elliptical. I havent gotten any significant results so far. I am managing diet from today on. before, perhaps I ate about 1300 calories a day. Here, the calculater says I need about 2100 cals (should I trust it?) so if I eat 1700 cals and workout I will lose weight?
Please help---I'm very frustrated with body.